Today, most of the crude oil (known as bitumen) produced from Canadian oil sands, particular from the Athabasca region of Canada, is obtained via surface mining followed by extraction with a water based system, based on a discovery made in the 1920s, which is also referred to as the Clark process. Following extraction of the bitumen from the oil sand, a frothy water-hydrocarbon mixture must be separated. The crude oil or bitumen product that is extracted, however, is too viscous to pump. Therefore, the bitumen is frequently diluted with an organic material or diluent to render the bitumen-solvent blend pumpable. This diluted bitumen is then sent to a facility for upgrading to the desired product mix. Such a process, despite many decades of process improvement work, remains energy intensive, requires significant quantities of water that must be cleaned for re-use, and generates bottoms (known as tailings) that contain high levels of fines.
Solids from the Clark process or tailings fines require long-term storage before the fines can become trafficable and suitable for reclamation. The Energy Resources Conservation Board (ERCB) of the Canadian province of Alberta has noted in Directive 074 (February, 2009) that “in past applications, mineable oil sands operators proposed the conversion of fluid tailings into deposits that would become trafficable and ready for reclamation. While operators have applied fluid tailings reduction technologies, they have not met the targets set out in their applications; as a result, the inventories of fluid tailings that require long-term containment have grown. With each successive application and approval, public concerns have grown.” In one region of interest, in Alberta, Canada, there are already several huge operations using this technology wherein the water requirements are supplied by the Athabasca River.
Hydrocarbon extraction processes have been considered as alternatives to the Clark process. For example, WO 2009/147622 discloses an oil extraction process that uses an extraction chamber and a hydrocarbon solvent rather than water to extract the oil from oil sand. The solvent is sprayed or otherwise injected onto the oil-bearing product, to leach oil out of the solid product resulting in a composition comprising a mixture of oil and solvent, which is conveyed to an oil-solvent separation chamber.
U.S. Pat. No. 4,347,118 discloses a solvent extraction process for tar sands wherein a low boiling solvent having a normal boiling point of from 20° to 70° C. is used to extract tar sands. The solvent is mixed with tar sands in a dissolution zone, the solvent:bitumen weight ratio is maintained from about 0.5:1 to 2:1. This mixture is passed to a separation zone in which bitumen and inorganic fines are separated from extracted sand, the separation zone containing a classifier and countercurrent extraction column. The extracted sand is introduced into a first fluid-bed drying zone fluidized by heated solvent vapors, so as to remove unbound solvent from extracted sand while at the same time lowering the water content of the sand to less than about 2 wt %. The treated sand is then passed into a second fluid-bed drying zone fluidized by a heated inert gas to remove bound solvent. Recovered solvent is recycled to the dissolution zone.
Although hydrocarbon extraction processes provide an advantage that water is not used in the extraction of the oil from the oil sand, thereby reducing environmental impact, a problem persists, however, in that hydrocarbon extraction has been difficult to control. For example, the degree of extraction of the oil from the oil sand has been difficult to control, as well as the ability to efficiently separate the solid material from the solvent and extracted oil. Such extraction processes are often quite time consuming, meaning they have been difficult to design at an acceptable commercial scale.